Just for clarity, I'm not necessarily looking to address it as a video device. If there was some way of rendering a bit image in .NET and then shifting it out across some GPIO pins, then that would be perfect.

Has anybody used any kind of small form-factor screen, attached as a HAT, with IoT?

I guess it doesn't have to be eInk / ePaper if the Pi / IoT ecosystem isn't geared up for that.